The present invention relates to internal combustion engines. In particular, the present invention relates to the flow of air-fuel mixture in an engine from a carburetor to a cylinder by way of an intake port of the cylinder head, and also the flow of cooling air around the cylinder head of the engine and the carburetor.
The cylinder head of an internal combustion engine includes an intake port into which an air-fuel mixture is delivered from the carburetor of the engine. The intake port is commonly formed from first and second channels that intersect one another at 90 (or approximately 90) degrees, and thus is L-shaped. Typically, the two channels are cylindrical or approximately cylindrical (or conical), e.g., such that the channels have circular or elliptical cross-sections. A carburetor end of the L-shaped intake port, at which is an opening of the first of the two channels, receives the air-fuel mixture from the carburetor. A cylinder end of the L-shaped intake port, at which is an opening of the other of the two channels, interfaces the interior of the cylinder of the engine and forms a valve seat for an intake valve governing the flow of the air-fuel mixture into the cylinder. An additional channel extends beyond the intersection of the first and second channels, parallel to the second channel, and forms a guide/support for the valve stem.
Manufacturing an intake port with this design is relatively simple to perform and therefore cost-effective. Formation of the intake port only requires the casting/diecasting or drilling (from perpendicular angles) of the two channels into the cylinder head. However, an intake port manufactured by way of low cost casting or drilling processes provides for imperfect flow characteristics of the air-fuel mixture within the intake port, which in turn can hinder performance of the engine. In particular, the inner 90 degree corner of the L-shaped intake port introduces a stall region in the flow of the air-fuel mixture. That is, due to the corner, the flow of the air-fuel mixture past the valve into the cylinder is slowed down near the corner. Consequently, the amount of air-fuel mixture that flows into the side of the cylinder proximate the inner 90 degree corner is reduced in comparison with the amount that flows into other portions of the cylinder. As a result, filling of the cylinder is incomplete and so the engine combustion is uneven and less efficient.
Alternate conventional ways of forming an intake port do not substantially resolve these problems and/or introduce other problems. For example, while it is possible to form an intake port from a pair of channels that are at greater than 90 degrees relative to one another (e.g., at 120 degrees), this does not substantially eliminate the problem of stalling of the flow of the air-fuel mixture near the inner corner formed by the intersection of the two channels. Additionally, the diecasting of passages at such obtuse angles is more difficult to perform and therefore more costly. Also for example, while it is possible to ameliorate the effects of the inner corner by grinding away the corner (or xe2x80x9cporting the headxe2x80x9d), such process is also relatively difficult and costly to perform and, in particular, is difficult to perform in a standardized, consistent manner.
Conventional engines also commonly suffer from problems relating to undesirable air circulation characteristics around the outside of the cylinder heads as well. Conventional cylinder heads typically are attached to the carburetors from which the air-fuel mixture is to be provided. This physical attachment/proximity can be undesirable insofar as the heat of the cylinder and cylinder head can be transferred to the carburetor and overheat the carburetor and negatively impact its performance. Indeed, due to the proximity of the carburetor and the cylinder head, it is possible for the heat of the cylinder head to affect the temperature and performance of the carburetor simply by way of the air flow that occurs around these components, particularly cooling air flow supplied by the engine fan.
It would therefore be advantageous if a new cylinder head assembly could be designed in which the flow of air-fuel mixture through the intake port was not significantly stalled, such that the air-fuel mixture was evenly delivered to the cylinder. It would additionally be advantageous if the new cylinder head assembly was designed to reduce the amount of heat transferred from the cylinder and cylinder head to the carburetor attached to the cylinder head. It would further be advantageous if the new cylinder head assembly was simple and not costly to manufacture.
The present inventors have discovered a component that, when coupled to a conventional cylinder head, reduces the stalling of the flow of air-fuel mixture through the intake port of the cylinder head and consequently improves the delivery of air-fuel mixture to the cylinder, thus improving engine performance. The component is specifically mounted to the cylinder head at the carburetor end of the L-shaped intake port, and includes a tongue that protrudes into the intake port. The tongue extends along a side of the first passage of the L-shaped intake port from the carburetor end up to the inner 90 degree corner of the L-shaped intake port. The surface of the tongue, along with the remaining exposed portion of the first passage, forms a modified passage extending from the carburetor end to the inner 90 degree corner of the L-shaped passage. The surface of the tongue is tapered and/or rounded as it approaches the inner 90 degree corner such that, given the addition of the tongue, stalling of the flow of air-fuel mixture is largely or entirely eliminated. By employing a tongue to modify the L-shaped intake port, the L-shaped intake port can still be manufactured using conventional, low-cost casting or drilling techniques.
The shape of the modified passage created by the first passage and tongue can vary depending upon the embodiment. In some embodiments, the first passage has a tapered surface opposite the surface at which the tongue is to be positioned, such that the first passage is elliptical in cross-section and decreases in cross-sectional area as one proceeds toward the inner 90 degree corner. In certain of these embodiments, the addition of the tongue tends to create a modified passage that is largely cylindrical and that intersects the second passage at greater than 90 degrees.
In certain embodiments, the component is attached to the carburetor end of the L-shaped intake port in between the cylinder head and the carburetor, which are both attached to the component on opposite sides of the component. The component is preferably manufactured from a heat resistant material such that heat transfer from the cylinder head to the carburetor through the component is limited. Further, in some embodiments, the component includes a baffle that extends outward on either side of the interface between the carburetor and the cylinder head, further extends outward to curve over the carburetor, and further extends outward to curve under the cylinder head. Thus, air flow from the cylinder head to the carburetor is limited, and cooling air from the fan is primarily directed toward the cylinder head and away from the carburetor.
In particular, the present invention relates to a cylinder head assembly comprising a cylinder head and a component coupled to the cylinder head. The cylinder head includes a first port having a first passage linking a first end to an intersection, and a second passage linking a second end to the intersection, where the intersection includes an abrupt transition between the first and second passages. The component includes a tongue that protrudes into the first passage from the first end to proximate the intersection, where the tongue is positioned along at least a portion of an inner side of the first passage, and where the tongue is gradually-reduced in thickness at least proximate the intersection.
The present invention further relates to a component for implementation in an internal combustion engine, the component being positioned in between a cylinder head and a carburetor of the engine. The component includes means for protruding into a port of the cylinder head and limiting stalling of a flow of air-fuel mixture within the port.
The present invention additionally relates to a method of providing an air-fuel mixture from a carburetor to a cylinder of an internal combustion engine. The method includes providing a cylinder head with an L-shaped intake port formed by first and second channels that interconnect at an abrupt intersection, where a first end of the L-shaped intake port is coupled at least indirectly to the carburetor to receive the air-fuel mixture from the carburetor, and where a second end of the L-shaped intake port is coupled to the cylinder. The method further includes providing a tongue within the first channel of the L-shaped intake port between the first end and the intersection, where an internal volume of the L-shaped intake port that is open for conducting the air-fuel mixture is reduced by the tongue. The method additionally includes providing the air-fuel mixture from the carburetor to the first end of the L-shaped intake port, and directing the air-fuel mixture through the internal volume of the L-shaped intake port as reduced by the tongue. The method further includes communicating the air-fuel mixture past an open valve and into the cylinder, where an abruptness of the abrupt intersection between the first and second channels is reduced by the tongue.